The present invention generally relates to the use of curable resin treatment fluids in subterranean operations, and, more specifically, to the use of hardenable acid curable resin treatment fluids comprising hardenable acid curable resin compounds and acid esters, and methods of using these treatment fluids in subterranean operations.
Many petroleum-containing formations also contain unconsolidated granular mineral material such as sand or gravel. After completion, production of fluids from the formation causes the flow of the particulate matter into the wellbore, which often leads to any of several difficult and expensive problems. Unconsolidated subterranean zones include those which contain loose particulates that are readily entrained by produced fluids and those wherein the particulates making up the zone are bonded together with insufficient bond strength to withstand the forces produced by the production of fluids through the zone. Sometimes a well is said to “sand up”, meaning the lower portion of the production well becomes filled with sand, after which further production of fluid from the formation becomes difficult or impossible. In other instances, sand production along with the fluid results in passage of granular mineral material into the pump and associated hardware of the producing well, which causes accelerated wear of the mechanical components of the producing oil well. Sustained production of sand sometimes forms a cavity in the formation which collapses and destroys the well.
Conventional treatment methods involve treating the porous, unconsolidated mass sand around the wellbore in order to cement the loose sand grains together, thereby forming a permeable consolidated sand mass which will allow production of fluids but which will restrain the movement of sand particles into the wellbore. These procedures create a permeable barrier or sieve adjacent to the perforations or other openings in the well casing which establish communication between the production formation and the production tubing, which restrains the flow of loose particulate mineral matter such as sand.
Oil or gas residing in the subterranean formation may be recovered by driving the fluid into the well using, for example, a pressure gradient that exists between the formation and the wellbore, the force of gravity, displacement of the fluid using a pump or the force of another fluid injected into the well or an adjacent well. The production of the fluid in the formation may be increased by hydraulically fracturing the formation. To accomplish this, a viscous fracturing fluid may pumped down the casing to the formation at a rate and a pressure sufficient to form fractures that extend into the formation, providing additional pathways through which the oil or gas can flow to the well. A proppant is a solid material, typically treated sand or man-made ceramic materials, designed to keep an induced hydraulic fracture open, during or following a fracturing treatment. It is added to the fracturing fluid. After the fracturing procedure has been completed, it may be desirable to consolidate the proppant materials.
Typical sand consolidation treatments use plastic resins, and are not entirely satisfactory. Resins tend to reduce the permeability of the consolidated formation below acceptable levels. In addition, resins are relatively costly on a unit volume basis and can be operationally very difficult to properly place in the formation. Certain resins, such as furan based resins, require a high temperature to initiate the curing of the resin. Additionally, when acids are mixed with furan-based resins, a rapid, exothermic reaction may occur. Typically, resins must separate from the catalysts until the moment they are used in the wellbore treatment, thereby creating a two-part system. The acids may further cause a degradation of the fluid viscosity.
Accordingly, an ongoing need exists for catalysts that may be added to and stored with resins without concern of rapid and exothermic reactions, and catalysts that can cure the resins at low temperatures when placed downhole for consolidating sand and other proppant particles in subterranean formations.